The aim of the study is to analyze the relationship between the decreases of FEF50% - on the one hand, and radiologically verified compensatory lung emphysema among workers, exposed to mineral dust at the work place - on the other. A case control study among 480 quartz-exposed underground miners, 120 asbestos-exposed workers, and 121 individuals without dust exposure was performed. The average age of the examined workers was 42.82 years, and the average duration of the dust exposure was 14.01 years. A clinical examination, as well as a chest radiography (by ILO’80), and spyrometry of all persons were done. We used SPSS software and one-way ANOVA. There was a significant decrease of the mean of FEF50% in cases with lung emphysema, accounted on the chest radiography (by ILO’80). We assume that the compensatory emphysema and reduction of FEF50% is associated with the formation of initial interstitial pulmonary fibrosis among workers exposed to mineral dust over a long period and in patients with pneumoconiosis. Conclusion 1. The decrease of FEF50% is related to radiologically established compensatory lung emphysema. 2. The investigation of FEF50%, combined with chest X-ray, is an appropriate constellation for periodical preventive medical check ups and assessment of health status for workers exposed to mineral dust.

E. Petrova, “Respiratory functional impairments in dust-exposed individuals,” in Proc. Twelfth National Conference of Young Specialists from the Hygienic and Epidemiological Services, Varna, Bulgaria, 1995.